1. Field of the Invention
This invention relates to filter material for use in removing by adsorption or absorption (sorbtion) undesirable matter from a fluid stream which passes through the filter material. Also disclosed are methods of making the filter material in a production setting.
2. Background Art
This application incorporates by reference U.S. Pat. Nos. 5,338,340 and 5,569,489.
In U.S. Pat. No. 5,569,489, I have disclosed methods of making filter material wherein sorbent particles or granules are incorporated into a fibrous mat during the formation of the mat. Further experimentation with such methods of making filter material has enabled me to make improvements in the methods which have resulted in the ability to produce in a production setting a wide variety of filter material ranging from about one inch in thickness for heavy duty applications down to about one-eighth inch thickness for light duty applications and wherein the sorbtive particles are retained in the mat without resorting to covering opposite faces of the mat with a layer of adhesive, thereby avoiding a high delta in pressure drop across the filter material.
Before development of the methods disclosed herein, in order to prevent the sorbtive particles, for example activated carbon, from falling out of the mat, opposite faces of the mat would be sprayed or roll coated with adhesive. While this helped lock the sorbtive particles in the mat, though not as completely as desired, it caused a high pressure drop rendering the product unacceptable for some applications. The failure to lock the particles in the mat completely, rendered the mat “dirty”, i.e., not clean enough for some applications.